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Soavtorji: Branko Alič, Matjaž Krajnc, Alenka Vesel, Urška Šebenik. Bibliografija: str. 10-12. Abstract.

Information on the reaction kinetics in the melt is a valuable prerequisite for a successful application of self-healing ability to benzoxazine-based thermosetting resins. The goal of this research was to develop a kinetic model of the Diels–Alder (DA) reaction in a molten state between N-phenylmaleimide (PMI) and benzoxazine-containing furan group (G-f). Rheological data were found to be of significant importance in the kinetic model development and interpretation. The increase in viscosity, the occurrence of side reactions, and equilibrium between DA and r-DA reaction were identified as possible reasons for the deceleration of reaction rate and limiting conversion. After a thorough investigation of the studied system, accompanied by the knowledge from the literature, the potential reason for the incomplete conversion of reactants was reduced to the crossover between chemically and diffusion-controlled reaction due to the increasing viscosity of reaction system. Accordingly, the kinetic model based on the combination of Rabinowitch equation and Chern–Poehlein model was used to accurately describe the progress of the studied reaction in the molten state.

Diplomska naloga obravnava polimerne gelske elektrolite (PGE), ki so zaradi varnejše uporabe, vedno bolj popularni pri prenosnih elektronskih napravah in napravah za shranjevanje električne energije. Gelska struktura PGE zmanjša njihovo vnetljivost in onemogoča razlitje. S tem postanejo veliko bolj varni za uporabo od tekočih elektrolitov. Njihova glavna slabost je nizka prevodnost, zaradi višje viskoznosti. Sestavljeni so iz polimerne matrike, topila in elektrolita. Polimerna matrika ima največji vpliv na mehanske lastnosti PGE, ki so pogojene predvsem z uporabljenim polimerom. Lastnosti polimerne matrike lahko spremeni dodatek mehčal. To so majhne organske molekule, ki vplivajo na kohezijske sile med molekulami. V diplomski nalogi sem preiskoval vpliv koncentracije elektrolita, polimera, mehčala in vpliv molske mase polimera na prevodnost PGE na osnovi polivinil alkohola (PVA). Molska masa PVA na prevodnost ne vpliva, medtem ko njena koncentracija v začetku zaradi gibanja segmentov polimernih verig povečuje prevodnost, kasneje pa jo zaradi višje viskoznosti zavira. Koncentracija elektrolita zaradi višje disociacije prav tako zvišuje prevodnost, po doseženem vrhu pri 0,66 g/L pa jo začne zavirati. Razlog za to najdemo v znižanju disociacije ob veliki koncentraciji elektrolita. Koncentracija mehčala na prevodnost ne vpliva, vpliva pa njegov dodatek, ki tisočkrat zviša prevodnost. The thesis deals with polymer gel electrolytes (PGE), which are increasingly popular in portable electronic devices and electrical energy storage devices due to their safer use. The gel structure of PGEs reduces their flammability and prevents spillage. This makes them much safer to use than liquid electrolytes. Their main disadvantage is low conductivity, due to higher viscosity. PGE consist of a polymer matrix, a solvent and an electrolyte. The polymer matrix has the greatest influence on the mechanical properties of the PGE, which are mainly determined by the used polymer. The properties of the polymer matrix can be changed by the addition of plasticizers, so that small organic molecules affect the cohesive forces between the molecules. In the thesis, I investigated the influence of the concentration of the electrolyte, polymer, softener, and the influence of the molar mass of the polymer on the conductivity of PGE based on polyvinyl alcohol (PVA). The molar mass of PVA does not affect conductivity, while its concentration initially causes conductivity due to the movement of polymer chain segments, but later inhibits it due to higher viscosity. Electrolyte concentration also increases conductivity due to higher dissociation, but after reaching a peak at 0.66 g/L, it begins to decrease. The reason for this can be found in the reduction of dissociation at a high electrolyte concentration. The concentration of the plasticizer does not affect the conductivity, but its addition does, which increases the conductivity by a thousand.

Grafen-oksid je predmet številnih raziskav. Zaradi svojih izrednih električnih, optičnih in kemijskih lastnosti je njegova uporaba zelo razširjena. Eno izmed teh področij je tudi biosenzorika, kjer se je GO izkazal kot material, ki lahko doprinese k številnim izboljšavam. Raziskovanje v diplomskem delu je usmerjeno v materiale na osnovi grafen-oksida, ki se uporabljajo pri načrtovanju in izdelavi bioloških senzorjev. Biosenzorji imajo ključni pomen v medicini, klinični analizi in splošnemu spremljanju zdravja. Zato so njihove lastnosti in zmožnosti nenehno raziskujejo in izboljšujejo. V delu sem raziskovala lastnosti GO materialov in njihovo aplikacijo v bioloških senzorjih. Podrobneje sem preučila raziskave, kjer se grafen-oksid uporablja za različne vrste biosenzorjev, kot so biosenzor za zaznavo lizocima, za zaznavo rakavih celic in zaznavo patogena. Predstavljeno je tudi splošno delovanje senzorjev in njihove najpomembnejše lastnosti. Graphene oxide is the subject of many researches. Due to his extraordinary electrical, optical and chemical properties its use is widespread. One of the areas is also biology, where GO has proven to be a material that can contribute many improvements in biosensors. The research is focused on materials based on graphene oxide, which are used in design and manufacture of biological sensors. Biosensors are very important in medicine, clinical analysis and general health monitoring. Therefore, their properties and capabilities are constantly being researched and improved. In my work, I researched the properties of GO materials and their application in biological sensors. I studied in more detail the research where graphene oxide is used for different types of biosensors, such as biosensor fort the detection of lysozyme, for the detection of cancer cells and the detection of a pathogen. In the work there are also presented operation biological sensors and their most important properties.

Z nenehnim razvojem biokompatibilnih, biorazgradljivih in nestrupenih materialov za hidrogele se je njihova uporaba na področju medicine in farmacije močno razširila. Zaradi pomembnosti teh materialov in njihovih visokih stroškov pridobivanja so potrebne metode karakterizacije, ki porabijo manj materiala za vzorce in so nedestruktivne za vzorca. Pomemben sklop lastnosti, ki so neposredno povezane z njihovo uporabo in vzdrževanjem v organizmu, so reološke lastnosti teh materialov. V svojem magistrskem delu sem preučeval vplivi staranja gela in masne vsebnosti dispergirane faze v nizu suspenzij na bazi nanofibrilirane celuloze. Vplivi sem preučeval s primerjavo dvema metodama – reometra, ki lahko karakterizira vzorce v volumnu mililitrov, in optične pincete, ki, kot mikroreološka metoda karakterizacije lahko karakterizira vzorce z volumnom v mikrolitrih, ali celo nanolitrih. Na podlagi poskusov in matematičnega modeliranja eksperimentalnih podatkov sem ugotovil, da staranje sistemov in masni delež dispergirane faze vplivata na reološke lastnosti sistemov. Poleg tega sem ugotovil, da rezultati obeh metod niso primerljivi med seboj v istem časovnem obdobju. Ugotovil pa sem tudi, da mikroreološke meritve z optično pinceto zagotavljajo dopolnilne informacije o reološkem in viskoelastičnem obnašanju heterogenih sistemov, ki so povezane s spremembami v mikrostrukturi suspenzije, in sicer na drugačni časovni skali, ki je ni mogoče zabeležiti z uporabo reometra za karakterizacijo sistemov. With the continuous advancement of biocompatible, biodegradable and non- toxic materials for hydrogels, their usage has greatly expanded in the fields of medicine and pharmaceuticals. The importance of those materials, combined with their high sourcing cost, invokes the need for characterization methods which consume less material for samples and are non-destructive to the sample. Meanwhile, an important set of properties that are directly connected to their application and maintenance in an organism are the rheological properties of such materials. In my master’s thesis, I studied the effects of ageing and weight percentage of the dispersed phase in a set of nanofibrilated cellulose suspensions, using a comparison of two methods – a rheometer, which measures the material in bulk quantities (in the range of milliliters), and optical tweezers, which is a method of microrheological measurement (in the range of micro and nanoliters). Based on the experiments and the fitting of the experimental data, I found out that the ageing of the systems and the weight percentage of the dispersed phase has an influence on the rheological properties of the systems. Further, I have found that the results from both methods were not comparable on the same timescale. However, I have also found out that microrheological measurements using optical tweezers provide complementary information on the rheological and viscoelastic behavior of heterogeneous systems related to changes in the suspension microstructure, on a different timescale, which is not possible to be recorded by using a rheometer to characterize the systems.

Razvoj industrije je poleg številnih ugodnosti in izboljšane kakovosti življenja prinesel tudi nekatere negativne spremembe. Eden izmed največjih izzivov je preprečevanje onesnaževanja okolja. Vsako leto se v okolje izpusti večje količine odpadne vode, ki vsebuje znatno količino okolju in zdravju škodljivih snovi. Problem predstavljajo predvsem težke kovine, barvila in farmacevtske učinkovine. Tovrstna onesnaževala so obstojna, niso biorazgradljiva, imajo sposobnost bioakumulacije in biomagnifikacije, so strupena, mutagena in kancerogena. Ena izmed najučinkovitejših metod za odstranjevanje onesnaževal iz vode je adsorpcija, ki poleg visoke učinkovitosti, cenovne ugodnosti in enostavne uporabe ne povzroča nastajanje stranskih produktov. V zadnjih letih številne raziskave obravnavajo adsorpcijo s hidrogeli zaradi številnih prednosti, kot so: biokompatibilnost, biorazgradljivost, možnost ponovne in enostavne uporabe in izdelave. V sklopu magistrske naloge sem preučevala optimalne parametre za pripravo sferičnih hidrogelnih delcev na osnovi alginata in sferičnih hidrogelnih delcev na osnovi alginata z dodatkom večplastnega grafen oksida (GO) z uporabo brizgalne črpalke. Spreminjala sem naslednje parametre: odstotek zamreževala (CaCl2), premer cevi brizgalne črpalke in hitrost pretoka natrijevega alginata skozi cev črpalke. Ugotovila sem, da na morfologijo sferičnih hidrogelnih delcev vplivata odstotek zamreževala in hitrost pretoka. Najnižji odstotek CaCl2, ki omogoča nastanek stabilnih hidrogelnih sfer je 0,43 m/v % in najvišja hitrost pretoka je 600 ml∙h-1. Po izbiri optimalnih parametrov za sintezo sferičnih hidrogelnih delcev sem preučevala adsorpcijske lastnosti alginatnega hidrogela. Kot adsorbat sem uporabila barvilo metilvijolično (MV) in sem določila vpliv različnih spremenljivk na adsorpcijo, kot so: pH vrednost, razmerje med maso hidrogela in volumnom raztopine barvila MV, začetna koncentracije barvila MV, odstotek zamreževala in dodatek večplastnega GO na adsorpcijo. Ugotovila sem, da je adsorpcija najučinkovitejša pri nižjem odstotku zamreževala (0,43 m/v %) in pri pH vrednosti 7. Prav tako sem ugotovila, da je adsorpcija barvila MV učinkovitejša, kadar hidrogel vsebuje GO in znaša 96 %. Visoko učinkovitost adsorpcije in visoko adsorpcijsko kapaciteto hidrogela z GO sem opazila samo pri nižji koncentraciji barvila (8 mg∙L-1). Pri višjih koncentracijah barvila je učinkovitejši alginatni hidrogel brez GO. Razlagam si, da v tem primeru GO predstavlja oviro za difuzijo barvila MV v notranjost hidrogela. V magistrski nalogi sem prav tako določila reološke lastnosti hidrogelov. Ugotovila sem, da alginatni hidrogel izkazuje psevdoplastične lastnosti, ki jih najboljše opisuje Carreau – Yasuda tokovni model. Za opis viskoelastičnih lastnosti alginatnega hidrogela je najustreznejši Maxwellov model, s pomočjo katerega je mogoče določiti velikost por hidrogela in gostoto zamreženja. Največjo velikost por sem določila za vzorec, ki vsebuje najnižji odstotek zamreževala (0,43 m/v %) in ne vsebuje GO. Velikost por tovrstnega vzorca je bila 6,89 nm. In addition to many benefits, rapid industrialization has also brought some negative changes. One of the biggest challenges is environmental pollution prevention. Large amount of wastewater is released in the enviroment every year, which contains a significant amount of harmful substances. Dyes, heavy metals and pharmaceutical ingredients are problematic, because they are perisitent, non-biodegradable, bioaccumulative, biomagnifying, toxic, mutagenic and carcinogenic. One of the most effective methods for removing pollutants from water is adsorption, which has many benefits, such as: easy use, does not cause a formation of by-products and its cheap. Therefore, in recent years many studies have adressed adsorption with hydrogels due to a number of advantages, such as: biocompatibility, biodegradability, reusability and it is easy to use and manufacture. In my master's thesis, the optimal parameters for synthesis of alginate hydrogel beads and alginate hydrogel beads with addition of few layer graphene oxide (GO) using injection pump are investigated. The parameters, such as: percentage of crosslinker (CaCl2), the diameter of injection pump pipe and the flow rate of sodium alginate throug injection pump were varied. The results showed, that morphology of alginate hydrogel beads is influenced by crosslinker percentage and flow rate. The lowest percentage of crosslinker that allows formation of stabile hydrogel beads is 0,43 m/v % and the maximum flow rate is 600 ml∙h-1. After selecting the optimal parameters for the synthesis of hydrogel beads, the adsorption properties of alginate hydrogel beads were studied. Organic dye methyl violet (MV) was used as adsorbate. Different variables that could affect the adsorption process, such as: pH value, hydrogel mass to MV solution volume ratio, crosslinker percentage and GO addition were investigated. According to results, adsorption was more effective at lower crosslinker percentages (0,43 m/v %) and at pH value 7. Furthermore, MV dye adsorption is more efficient when the alginate hydrogel contains GO, and is 96 %. High efficiency and high adsorption capacity of alginate hydrogel beads with GO were observed at lower concentration of MV dye (8 mg∙L-1). At higher concentrations of MV dye, GO represents barrier for the diffusion of MV dye into the hydrogel. In this thesis the rheological properties of algnate hydrogels were also studied. The alginate hydrogel exhibits the pseudoplastic properties, which is best described by Carreau – Yasuda flow model. To describe the viscoelastic properties of alginate hydrogel, the Maxwell model is the most suitable. Based on the parameters obtained by Maxwell model, crosslinking desity and pore size of hydrogel were calculated. The highest pore size was observed in the sample containing the lowest percentage of crosslinker (0,43 m/v %) and without GO. The pore size of this type of sample was 6,89 nm.

Nanokompozitni hidrogeli so sestavljeni iz polimera in nanodelcev, kot so glina, grafen in grafen oksid. Prisotnost nanodelcev izboljša mehansko odpornost in termično stabilnost hidrogelov. Trend zelene kemije spodbuja uporabo obnovljivih, netoksičnih, naravnih in biorazgradljivih polimerov, med katere spada tudi skleroglukan. Skleroglukan je naravni polisaharid, ki v vodnih raztopinah tvori fizikalno zamrežen hidrogel, ki je obstojen v širokem območju pH vrednosti in izkazuje psevdoplastične lastnosti. V svojem magistrskem delu sem preučeval vpliv dodatkov plastovitih nanodelcev na reološke lastnosti hidrogela iz skleroglukana. Izbral sem si naslednje dodatke: glino (Cloisite 30B, Cloisite Na+, Laponite RD), grafen in grafen oksid. Ugotovil sem, da vrsta in količina dodanega plastovitega nanomateriala vpliva na reološke lastnosti hidrogela iz skleroglukana. Na reološke lastnosti vpliva tudi staranje in sprememba pH vrednosti. Na osnovi rezultatov reoloških testov sem sklepal na vrsto interakcij med delci skleroglukana in nanodelci, ki imajo lahko hidrofilno bodisi hidrofobno naravo. Nanocomposite hydrogels are composed of polymer and nanoparticles, such as clay, graphene and graphene oxide. The presence of nanoparticles improves mechanical resistance and thermal stability of hydrogels. Green chemistry trend promotes the use of renewable, non-toxic, natural and biodegradable polymers, including scleroglucan. Scleroglucan is a natural polysaccharide that forms a physically cross-linked hydrogel in aqueous solutions, which is stable in a wide pH range and exhibits pseudoplastic properties. In my master’s thesis, I studied the influence of layered nanoparticles addition on the rheological properties of scleroglucan hydrogels. I selected the following additives: clay (Cloisite 30B, Cloisite Na+, Laponite RD), graphene and graphene oxide. I found out that the type and amount of layered nanomaterial addition affects the rheological properties of scleroglucan hydrogel. Rheological properties are also affected by aging and changes in pH values. Based on the results of the rheological tests, I concluded type of interactions between scleroglucan particles and nanoparticles, which may be hydrophilic or hydrophobic nature.

Pnevmatike so v motošportu ena od najpomembnejših komponent dirkalnika, saj predstavljajo edini fizični stik med podlago in dirkalnikom. Hitrost vožnje, taktične odločitve tekom tekmovanj in varnost zavisijo od njihovega delovanja. Pnevmatike za dirkanje so narejene za premagovanje krajših razdalj v čim krajšem času, kar pomeni, da sta obraba in staranje pnevmatik pomembna dejavnika pri dirkanju. Pnevmatike se obrabljajo s tanjšanjem tekalne površine, pogosta pa sta tudi pojava »graining« in »blistering«. Pnevmatike so sestavljene iz več komponent. Najpomembnejša je izbira kavčukov za gumene zmesi. V gumeno zmes dodajamo še polnila v obliki saj ali silike, procesna olja in dodatke, ki poskrbijo za boljšo obstojnost gumenih zmesi v pnevmatiki in učinkovitejšo ter hitrejšo vulkanizacijo pri njihovi izdelavi. Pomembna komponenta pnevmatik je tudi armatura, katera je sestavljena iz več jeklenih in različnih polimernih materialov. Izdelava pnevmatik poteka po točno določenem postopku, kjer se različne komponente pnevmatike najprej izdela posamično, vsako v svojem procesnim postopkom, nato pa se vse komponente združi, gumene zmesi zamreži in pregleda oziroma analizira. Racing tyres are one of the most important components of racing, as they are the only connection between bolide and track. Racing speed, tactical decisions and safety of drivers all depend on tyres functionality. Racing tyres are made to overcome short distances as fast as possible and, that means that tyre wear and tyre ageing are important factors in racing. Tyres wear physically with thinning of tread or with graining and blistering. Tyres are compounded of many components, most important of them being rubber. In rubber compound we also add fillers, such as soot or silica, process oils, and other accessories that enable longer lifespan of a tyre and more effective and faster vulcanization. Another important component of tyres is also carcass, which is made out of steel and polymers. Manufacturing of tyres is a strictly determined process in which all components are first made individually and are then brought together at the end of the process. At last, the rubber is vulcanized and inspected.

Diplomska naloga obravnava adsorpcijo barvil, govejega serumskega albumina (BSA) in težkih kovin na različno pripravljene laponitne hidrogele. Adsorpcija je proces, pri katerem se snovi, imenovane adsorbati, vežejo na površino snovi, imenovane adsorbenti. Adsorpcija barvil se je preučevala na laponitnih kapsulah, polivinil alkohol (PVA) laponitnem hidrogelu in polidopamin (PDA) laponitnem hidrogelu. Uporabljena barvila so bila kristalvijolično barvilo, metilensko modrilo in rodamin B, ki so kationska barvila, ter metil modro, kongo rdeče barvilo in metiloranž, ki so anionska barvila. Ugotovljeno je bilo, da se pri vseh treh hidrogelih na njihovo površino lažje adsorbirajo kationska kot anionska barvila. Takšna adsorpcija je predvsem posledica privlaka med pozitivno nabitimi molekulami barvil in trajnim negativnim nabojem na površini laponita. Adsorpcijo BSA proteina se je raziskovalo na hidrogelu iz hitozana, polivinil alkohola in laponita ter na hidrogelu iz polivinil alkohola, natrijevega alginata in laponita. Dokazano je bilo, da laponit zaradi svoje posebne strukture izboljša adsorpcijske lastnosti hidrogelom. Za adsorpcijo ionov težkih kovin je bil preučen polivinilpirolidon (PVP) laponitni hidrogel. Pri tem je dodatek laponita omogočil oblikovanje hidrogela. Ioni težkih kovin imajo pozitivni naboj in so se z lahkoto adsorbirali na negativna aktivna mesta na površini laponita. Pri vseh laponitnih hidrogelih poteka adsorpcija psevdo-drugega reda in s tem kemisorpcija. Mehanizem adsorpcije pri hidrogelih, kjer adsorpcija poteka le na površini laponita (laponitne kapsule, PVP laponitni hidrogel) sledi Freundlichovi izotermi, zato gre za heterogeno adsorpcijo. V primerih, kjer se adsorbati vežejo tudi s šibkimi Van der Waalsovimi vezmi na hitozan ali polivinil alkohol, mehanizem sledi Langmuirjevi izotermi in poteka monoslojna adsorpcija. Vse hidrogele je možno tudi regenerirati, kar jim daje dobro prednost za uporabo v različnih panogah. Thesis describes in detail adsorption of dyes, bovine serum albumin (BSA) and heavy metals onto prepared surfaces of laponite hydrogels. Adsorption is a process in which adsorbates bind onto the surface of adsorbents. Laponite capsules alongside polyvinyl alcohol – laponite hydrogel and hydrogel made from polydopamine and laponite were used for studying adsorption of dyes. Colorants used in the study were crystal violet, methylene blue and rhodamine B which are all cationic colorants and anionic dyes such as methyl blue, congo red and methyl orange. Results of the researches conducted showed that cationic colorants are more easily adsorbed onto the three hydrogels than anionic colorants. The described adsorption is a direct consequence of attraction between positively charged dye molecules and perpetual negative charge on the surface of the laponite. BSA protein adsorption was studied on hydrogel made from chitosan, polyvinyl alcohol and laponite and also on the hydrogel made from polyvinyl alcohol, sodium alginate and laponite. Researches show that laponite improves adsorption properties of hydrogels because of its special structure. For the purposes of heavy metal ions adsorption hydrogel made from polyvinylpyrrolidone and laponite was studied. The addition of laponite during the synthesis enabled the forming of hydrogel. Heavy metal ions have a positive charge and were easily adsorbed onto the negative centers on the surface of the laponite. Kinetics of the adsorption on all studied hydrogels are of the pseudo-second order which means that the type of adsorption is chemisorption. If adsorption takes place only on the surface of the laponite (lap capsules and polyvinylpyrrolidone-laponite hydrogel) the adsorption mechanism follows Freundlich isotherm which means that we have a heterogeneous adsorption. In cases where adsorbates also bind onto the chitosan or polyvinyl alcohol with weak Van der Waals bonds the adsorption mechanism follows the Langmuir isotherm and we have a monolayer adsorption. All of the abovementioned hydrogels have the ability to be regenerated which gives them a good advantage for use in different industries.

Hidrogeli so pametni materiali, ki so v zadnji letih dobili veliko pozornosti zaradi svojih lastnosti, kot so odzivanje na zunanje dražljaje, obstojnost, sposobnosti absorpcije, relativno visok elastični modul. Dandanes so izrednega pomena predvsem biorazgradljivi hidrogeli s širokim področjem uporabe. Tak primer so hidrogeli iz nanoceluloze. Hidrogele iz celuloznih nanovlaken ali nanokristalov se uporablja v senzoriki, kot sisteme za dostavo zdravil, dodatke v higienski in prehrambni industriji. Pomembni področji uporabe sta predvsem farmacija in medicina. Dodatki, kot so ogljikove nanocevke ali grafen se uporabljajo za izboljšanje lastnosti hidrogelov za specifično uporabo. Reološke lastnosti hidrogelov določujemo s pomočjo reometra, naprave, s katero merimo reološke parametre preiskovanega vzorca, kot so viskoznost, elastični modul in viskozni modul. V magistrski nalogi sem preučeval hidrogele iz TEMPO modificiranih celuloznih nanovlaken (CNF). Raziskoval sem reološke lastnosti hidrogelov TEMPO CNF z dodanimi tremi različnimi vrstami grafenskih nanoploščic. Uporabil sem nemodificiran grafen, grafen modificiran z amino skupinami in grafen modificiran s karboksilnimi skupinami. Določil sem vpliv staranja in vpliv deleža posameznega grafena na reološke lastnosti TEMPO CNF hidrogelov. Ugotovil sem, da se hidrogelom TEMPO CNF s časom povečuje viskoznost in narašča elastični modul kot posledica spreminjanja mikrostrukture hidrogelov, urejanja celuloznih verig s časom in tvorba vodikovih in van der Waalsovih vezi v hidrogelu. Zelo majhno razliko sem opazil pri rezultatih reoloških meritev pri preučevanju vpliva deleža grafena. S konduktometrično titracijo sem pokazal, da je bila koncentracija amino in karboksilnih skupin na modificiranih grafenih nizka, grafen modificiran s karboksilno skupino je vseboval 0,042-0,045 mmol/g -COOH skupine, grafen modificiran z amino skupino pa 0,979 mmol/g -NH_2 skupine. Opazil sem povišanje viskoznosti z višjo vsebnostjo posameznega grafena kot posledica višjega deleža nezvezne faze v suspenzijah. Dodatno sem preučil še vpliv pH vrednosti na reološke lastnosti hidrogelov TEMPO CNF. Ugotovil sem opazno višje vrednosti viskoznosti in elastičnega ter viskoznega modula pri hidrogelih s pH = 3. Možen razlog za to je izločanje vode, zmanjšanja odboja med polimernimi verigami in aglomeracija le teh zaradi prevladovanja van der Waalsovih vezi med verigami. Pri suspenzijah TEMPO CNF s pH = 11 sprememb v reoloških lastnosti nisem opazil. Reološke meritve so pokazale podobne rezultate kot pri pH = 7. Pri raziskovanju sem tako uspel določiti vpliv staranja, vpliv različno modificiranih grafenov in pH vrednosti na reološke lastnosti TEMPO CNF hidrogelov. Upam, da bo moje delo pripomoglo k nadaljnemu raziskovanju kompozitnih hidrogelov na osnovi TEMPO CNF in uporabi le-teh v novih aplikacijah. Hydrogels are smart materials, which in recent years received plenty of attention due to their excellent properties, such as response to stimuli, durability, capability of adsorption and relatively high storage modulus. Nowadays, great emphasis is put on biodegradable hydrogels with wide aspect of applications. Such examples are nanocellulose hydrogels, which are made from cellulose nanofibrils or nanocrystals, and can be used in various fields such as sensors, drug delivery systems and additives in food and health industry. Two of the most important fields for hydrogel applications are medicine and pharmacy. Nanofillers such as carbon nanotubes and graphene are used to improve hydrogel properties, so they can be used in specific applications. Rheological properties of hydrogels are measured by rheometers, which are used to measure rheological parameters such as viscosity, storage and loss moduli. In my master’s thesis hydrogels made of TEMPO modified nanocellulose are investigated. Three different graphene nanoparticles were added to TEMPO CNF suspensions graphene, graphene modified with amino groups and graphene modified with carboxyl groups. Firstly, I investigated the effect of aging of TEMPO CNF suspensions with specific additive and the influence of the amount of specific additive on rheological properties. The results showed higher viscosity and storage modulus of TEMPO CNF hydrogels over time. The reason for such behaviour is the microstructural change in suspensions, the arranging of nanocellulose chains over time and the creation of hydrogen and van der Waals bonds inside the hydrogel. Results from rheological measurements did not show major differences when comparing the effect of concentration of specific graphene on rheological behaviour of hydrogels. Later on, I was able to explain these results with conductometric titration. The amount of amino and carboxyl groups was low, there was between 0,042 – 0,045 mmol/g of -COOH groups in graphene modified with carboxyl groups and 0,979 mmol/g of -NH_2 groups in graphene modified with amino groups. I was able to obtain an increase in viscosity with higher amount of each graphene, which was the consequence of increase of dispersed phase in hydrogels. In addition, I researched the effect of pH value on TEMPO CNF hydrogels. Rheological results showed the increase in viscosity, elastic and storage moduli in acidic environment pH = 3. The reason for such behaviour could be water elimination from hydrogels as well as weaker repulsion between polymer chains. Nanocellulose chains also started to agglomerate due to the van der Waals interactions. Rheological behaviour of hydrogels at pH = 11 was similar to hydrogels with pH = 7. Furthermore, I concluded that higher pH does not affect the rheological behaviour of TEMPO CNF hydrogels. In my research, I managed to determine the effect of aging, the effect of modified graphene nanoplatelets addition, and the effect of pH value on the rheological properties of TEMPO CNF hydrogels. I hope my work will help with further research of TEMPO CNF composite hydrogels and the use of these smart materials in various new applications.

Polimerni materiali so s pospešenim razvojem tehnologije in industrije v zadnjih letih pridobili pomemben status v našem vsakdanjem življenju. Kljub mnogim prednostim, ki jih prinašajo polimerni materiali (nizka gostota, visoka trdnost, prikladnost večstranske uporabe...), predstavljajo veliko grožnjo našemu ekosistemu. Kot odpadek predstavljajo velik izziv, saj je pred postopki njihove razgradnje potrebno nadzorovano ravnanje z odpadkom (sortiranje). S tem razlogom je v zadnjem času moč zaznati razvoj na področju iskanja trajnostnih rešitev uporabe polimernih materialov v zunanjem okolju. V diplomski nalogi sem opisal dva pristopa, ki stremita k tem rešitvam. Prvi pristop temelji na kompozitnih materialih, ki so sestavljeni iz dveh ali več komponent, katere so izbrane na podlagi individualnih lastnosti, za katere želimo, da se ohranijo oziroma izrazijo v novonastalem kompozitu. Z ustrezno sestavo in procesom izdelave kompozita ima ta izboljšano zmogljivost oziroma boljšo funkcionalnost od individualnih osnovnih komponent. Drugi pristop, ki sem ga predstavil je samoceljenje polimernih materialov. Samoceljenje je lastnost nekaterih pametnih materialov, za katere je značilno, da se odzivajo na zunanje dražljaje. Material s sposobnostjo samoceljenja lahko definiramo kot material, ki ob nastali poškodbi takoj in avtonomno obnovi poškodovano mesto. Oba pristopa sta osredotočena na podaljševanje življenjske dobe polimernih materialov. S tem se v praksi izognemo raznim okvaram, popravilom in menjavi delov ter s tem zagotovimo trajnost produkta na področjih, kjer je to pomembno. V sklopu svojega diplomskega dela sem princip obeh pristopov povzel na primeru izdelave ter praktične uporabe specifičnega polimernega materiala s sposobnostjo samoceljenja, ki je ojačan z ogljikovimi vlakni (CFRP). With recent rapid development of technology and industry, polymeric materials have gained an important status in our everyday life. Despite many advantages, that polymeric materials are providing (low density, high strength, suitability of multilateral use…), they represent a significant threat to our ecosystem. As a form of waste, they represent a great challenge because the procedures of their decomposition demand controlled waste management (sorting). For that reason, it is possible to detect recent developments in the search for sustainable solutions in the field of polymeric materials applied in external environment. In my thesis I described two approaches, that strive for these solutions. The first approach is based on composite materials, that are composed of two or more components, which are selected on the basis of individual properties that we want to preserve or express in the newly formed composite. With the appropriate composition and manufacturing process of the composite, the performance and functionality of individual basic components are improved. The second approach I presented is self-healing of polymeric materials. Self-healing is a property of some smart materials, for which it is typical to respond to external stimuli. Material with the ability of self-healing can be defined as a material that with the occurrence of an injury, immediately and autonomously restores the damaged area. Both approaches are focused on the extension of longevity of polymeric materials. In practice, this allows us to avoid various defects, repairs and replacements of parts, thus ensuring the durability of the product in areas where it is of importance. Within my thesis, I have summarized the principle of both approaches with an example of manufacture and practical use of a specific polymeric material with self-healing ability, reinforced with carbon fiber (CFRP).

Ogljikova vlakna so snovi, zgrajena iz ogljikovih atomov in imajo izjemne lastnosti, predvsem, ko sestavljajo kompozit. Njihova izdelava je zahtevna, toda končni produkt je kakovosten in zaradi tega dosega tudi visoke cene na trgu. Ogljikova vlakna so kar petkrat močnejša od železa, imajo visoko trdnost in so korozijsko odporna. So odlično električno prevodna, imajo visoko natezno trdnost in nizek koeficient toplotnega raztezka. Niso škodljiva za človeka in kar je skoraj najboljša lastnost, so nevnetljiva. Čeprav so ogljikova vlakna nevnetljiva, je vnetljivost še vedno velik problem, ko ogljikova vlakna združujemo v polimerne kompozite. Poznamo tri najpogostejše polimerne osnove, ki se uporabljajo v kompozitih. To so epoksi, vinilester in poliesterska smola (poliesterska smola je le redko uporabljena z ogljikovimi vlakni). Vsak kompozit ima polimerno osnovo, ki je vnetljiva, zato se za visoko stopnjo nevnetljivosti, kompozitom dodajajo snovi, ki vnetljivost zavirajo. Pravimo jim zaviralci gorenja. Zaviralce gorenja lahko nanašamo v kompozit na različne načine. Lahko jih vmešamo v polimer med procesom izdelave, lahko jih kemijsko vgradimo v glavno polimerno verigo. Uporabimo lahko tudi zaviralce gorenja, ki se nanašajo kot zaščitna plast ali pa sami od sebe tvorijo zaščitno last, ko pridejo v stik z dovolj visokimi temperaturami. Zaviralce gorenja v splošnem delimo na fosforjeve, dušikove, halogenske, intumescenčne ter anorganske. Halogenski zaviralci gorenja temeljijo na dveh elementih, kloru in bromu, anorganski pa na aluminiju in magneziju. Anorganski zaviralci gorenja večinoma dodajamo le kot katalizatorje, da pospešijo delovanje drugih zaviralcev gorenja, ki so dodani kompozitu. Intumescenčni zaviralci gorenja ob povišanih temperaturah tvorijo zaščitno plast, ki varuje kompozit pred vžigom in razpadom. Za polimerne kompozite z ogljikovimi vlakni se večinoma uporabljajo halogenski in fosforjevi zaviralci gorenja. Prav fosforjevi zaviralci gorenja so začeli nadomeščati halogenske predvsem zato, ker so halogenski zaviralci gorenja škodljivi za človeka in okolje. Učinkovitost zaviralcev gorenja lahko določamo z različnimi tehnikami. Navadno merimo mejno vrednost kisika, to je koncentracija kisika, pri kateri snov še gori, lahko izvedemo skupino testov UL-94 ali pa s kalorimetrijo izmerimo sproščanje toplote in z rentgensko fotoelektronsko spektroskopijo spremljamo sestavo kompozita. Z dodajanjem zaviralcev gorenja kompozitnim materialom, se soočamo tudi z nevšečnostmi. Če pride do vžiga materiala in zaviralec ni učinkovit, lahko pride do učinka svečnega stenja, kjer gori polimer na ogljikovih vlaknih, vse dokler gorenje ni umetno prekinjeno oz. zmanjka goriva. Problem nastane tudi v polarnosti zaviralcev, kajti bolj polaren zaviralec gorenja kot polimerna osnova oslabi strukturo kompozita in privede do slabših mehanskih lastnosti. Danes se v kompozitih z ogljikovimi vlakni uporablja epoksi smola. Ker so materiali, zgrajeni iz epoksi smole lahki, lahko nadomestijo druge, prej težje materiale, kar je uporabno predvsem v letalski in avtomobilski industriji. Sprva so se takšnim kompozitom dodajali halogeni zaviralci gorenja, danes pa se zaradi nevarnosti vedno bolj uporabljajo fosforjevi. Potrebno je dobro poznati tako lastnosti zaviralcev gorenja kot tudi kompozita, da lahko dosežemo dobro odpornost proti vnetljivosti in tako še izboljšamo lastnosti polimernim kompozitom z ogljikovimi vlakni. Carbon fibres mainly consist of carbon atoms and they have some outstanding properties, especially when it is integrated in a composite. Although the production of carbon fibres is complex, the final product has great quality, which is why carbon fiber materials are expensive in the market. Carbon fibres are five times stronger than iron as well as rigid and corrosion resistant. Electric conductivity of carbon fibres and their tensile strength are high and thermal expansion coefficient is low. They are not poisonous for people in addition to not being flammable, which is one of their best features. Flammability, however is still a very big problem, when carbon fibres are put into polymer composites. There are three main polymer matrices, which can be used in polymer composites: epoxy resin, vinylester resin and polyester resin , which is rarely used with carbon fibres. Since almost every polymer has a polymer matrix which is flammable, special materials are added to the composites in order to make them non-flammable. They are called flame retardants and they can be integrated into composites in different ways. They can either be added to polymer matrix during the production process or they can be integrated in the main polymer chain. Flame retardants, which are added as protective coating or which form protective coatings during the exposure to high temperatures can also be used. In general, flame retardants can be divided to phosphorous, nitrogen, halogen, intumescent and inorganic flame retardants. Halogen flame retardants mainly contain one of two elements (chlorine or bromine) and inorganic flame retardants are generally made of aluminium or magnesium. Inorganic flame retardants are mostly used as catalysts, so they speed up the effect of other flame retardants added to the composite. Intumescent flame retardants create a protective layer at high temperatures, which protects composite from ignition and degradation. Mainly halogen and phosphorus flame retardants are used for polymer composites with carbon fibres. Since halogen retardants appear to be harmful to people and to the environment, phospohorous flame retardants started to be used as a substitute. Effectiveness of flame retardants can be determined by using various techniques. Most commonly the limiting oxygen index, and shows the percentage, where material still burns. In addition group of UL-94 tests can be performed or determine heat release with calorimetry or we can watch a chemical composition of product with x-ray photoelectron spectroscopy. Because of the addition of flame retardants to composite materials, several problems emerge. If the ignition of material happens and the flame retardants are not effective, a candlewick effect could happen. This means that the polymer is burning on carbon fibres until fire is turned down artificially or the fuel runs out. Another problem occurs in the polarity of flame retardants if flame retardant is more polar than polymer matrix, structure of composite becomes weak, which leads to bad mechanical properties. Nowadays, epoxy resin is mostly used in polymer composites with carbon fibres. Materials from such substances can replace other, heavier materials, which is very useful in aviation and automobile industry. Firstly, halogen flame retardants were added to such composites, and because halogen flame retardants are toxic, more and more phosphorus flame retardants are used. Properties of flame retardants and composites have to be well researched, so that good flame retardancy can be reached and that is how polymer composites with carbon fibres properties are even improved.

V tem magistrskem delu je bila raziskana možnost sintetiziranja cenovno ugodne nenasičene poliestrske smole z uporabo diciklopentadiena prek Diels-Alderjeve reakcije za abrazijsko odporne poliestrske kompozite. Ta smola je bila primerjana s smolo s tetrahidroftalnim anhidridom in smolo z izoftalno kislino. Smole so bile okaraterizirane s FT-IR in NMR spektroskopijo. Termične lastnosti so bile določene z DSC-analizo. Mehanske lastnosti so bile določene s tritočkovnim upogibnim testom in HDT-testom. Abrazijska odpornosti je bila testirana s Taber abraserjem. Ugotovljeno je bilo, da je rezultat abrazijske odpornosti smole s diciklopentadienom boljši od smole z izoftalno kislino, a slabši od rezultata smole s tetrahidroftalnim anhidridom. Z ekonomskega vidika je smola z diciklopentadienom cenejša od smole s tetrahidroftalnim anhidridom zaradi cene surovin. Proces sinteze se bistveno ne razlikuje, zato ne vpliva na ceno končnega proizvoda. The synthesis of a cost efficient unsaturated polyester resin via Diels Alder reaction with dicyclopentadiene for abrasion resistant composites was examined. Resin with dicyclopentadiene was compared to a resin with tethrahydrophthalic anhydride and a resin with isophthalic acid. Resins were characterised by FT-IR and NMR spectroscopy. Thermal properties were determined by DSC analysis. Mechanical properties were determined by three-point flexular test and HDT test. Abrasion resistance was tested by Taber abrasion test. Results suggested that the resin with dicyclopentadiene has better abrasion resistance in comparison with the resin with isophthalic acid. However, it has worse abrasion resistance than the resin with tethrahydrophthalic anhydride. From economic point of view it can be stated that the resin with dicyclopentadiene is cheaper than the resin with tethrahydrophthalic anhydride. This is due to lower prices of raw materials. Process of synthesis of the two resins is very similar and thus does not affect the price of the resin.

Hidrogeli imajo veliko aplikacij v različnih procesih, od industrijskih do bioloških. Obstajajo številni izvirni in pregledni članki, osredotočeni na sintezo, lastnosti in uporabo hidrogelov. V diplomski nalogi so zajete različne aplikacije v biomedicini. Hydrogels are used in numerous and various processes ranging from industrial to biological applications. There are a lot of original papers and reviews focused on the proprieties, synthesis and applications of the hydrogels. In the diploma work the various biomedical applications of hydrogels are covered.

Namen naloge je predstaviti reverzibilno zamrežene poliuretane z aromatsko pinakolno enoto, ki vsebuje reverzibilno C-C vez. V obravnavani študiji so znanstveniki sintetizirali PU na osnovi pinakola (P1) ter za potrditev lastnosti P1 sintetizirali in testirali še podobne poliuretane (P2, P3), ki pa se med seboj razlikujejo v sestavi in po lastnostih. Visoko žilavost PU na osnovi pinakola pripisujejo visoki energiji C-C vezi, ki pada z dolžino vezi zaradi elektronskih in steričnih učinkov. V zmernih pogojih (primerna aktivacijska energija cepitve vezi) se vezi v PU na osnovi pinakola lahko razcepijo in znova povežejo. Mešanje in preurejanje mrež vodi v celjenje razpok. Temperatura steklastega prehoda poliuretana P1 je bila določena z dinamično mehansko analizo (DMA) preko izračuna modula (elastični E', viskozni E'') materiala in tan δ. Ugotovljeno je bilo, da za reverzibilno reakcijsko procesiranje P1 ni potrebna kontrola temperature. Najpomembnejši korak pri sintezi stimulativno odzivnega polimera P1 je bil predhodna sinteza hidroksi funkcionaliziranega aromatskega pinakola ter njegova vključitev v zamrežen poliuretan. The aim of the thesis is to present reversibly crosslinked polyurethanes with an aromatic pinacol unit containing a reversible C-C bond. In the study in question, the scientists synthesized PU based on pinacol (P1) and synthesized and tested similar polyurethanes (P2, P3) to confirm the properties of P1, but they differ in composition and properties. The high toughness of pinacol-based PUs is attributed to the high energy of the C-C bond, which decreases with bond length due to electronic and steric effects. Under moderate conditions (appropriate bond cleavage activation energy), the bonds in a pinacol-based PU can split and reconnect. Mixing and rearranging the nets leads to the healing of the cracks. The glass transition temperature of polyurethane P1 was determined by dynamic mechanical analysis (DMA) through the calculation of the modulus (elastic E', viscous E'') of the material and tan δ. It was found that no temperature control is required for reversible P1 reaction treatment. The most important step in the synthesis of the stimulus-responsive polymer P1 was the preliminary synthesis of hydroxy-functionalized aromatic pinacol and its incorporation into cross-linked polyurethane.

Problem velike porabe fosilnih goriv in elektrike za delovanje klimatskih naprav za ogrevanje prostora se lahko reši z nadomeščanjem z materiali za shranjevanje energije. Določeni materiali absorbirajo in sproščajo toplotno energijo kadar je to potrebno. Najugodnejši so materiali za latentno shranjevanje energije, saj se pri tem shrani toplota potrebna za spremembo temperature, kot tudi toplota potrebna za spremembo agregatnega stanja spojine, ki spreminja agregatno stanje/fazo (angl. Phase change materials - PCM). Temperatura tališča PCM spojine določa področje uporabe kompozitnega materiala, kar pomeni, da so za uporabo v stanovanjskih objektih najbolj ugodne PCM spojine, ki imajo temperaturo tališča v območju sobne temprature (25 ℃), kar so najpogosteje organske spojine, kot so na primer maščobne kisline ali parafinski voski. Omenjene spojine morajo biti ustrezno vgrajene v nosilni material, da bi učinkovitost bila čim višja in, da ne bi prišlo nastanka požara, saj so organske spojine vnetljive. Ustrezna metoda vgrajevanja je stabiliziranje PCM spojine v nosilni material pri povišani temperaturi, ki se potem ohladi pod temperaturo steklastega prehoda. Kompozitni materiali za latentno shranjevanje toplote imajo nizko toplotno prevodnost in se jim zaradi tega dodajajo dopanti na osnovi ogljika. Poleg izboljšane toplotne prevodnosti, dopanti zagotavljajo tudi boljšo stabilnost PCM spojine v nosilnem materialu. V diplomskem delu sta opisana oba primera uporabe dopantov v kompozitnih materialih za latentno shranjevanje energije. Obravnavane so predvsem morfologija, termične in mehanske lastnosti materialov, ter toplotna prevodnost. Rezultati pridobljeni iz strokovne literature so pokazali, da so kompozitni materiali za latentno shranjevanje energije stabilni po večjem številu ciklov segrevanja in ohlajanja, temperatura tališča in temperatura steklastega prehoda nosilnega materiala se ohranjata in sta neodvisna od koncentracije dopantov. Nosilni materiali so stabilni pri temperaturi tališča PCM spojine, kar pomeni, da jo lahko zadržijo, ko je v tekočem stanju in preprečijo puščanje. Količina shranjene latentne energije je dovolj visoka za praktično uporabo in znaša med 100 J/g in 200 J/g, odvisno od deleža posameznih komponent. V primeru mešanice 0,8 ut.% grafen oksida z 19,2 ut.% nosilnega materiala (mešanica lesnega prahu in poliuretana) in 1,2 ut.% grafen oksida z 18,8 ut.% nosilnega materiala se je toplotna prevodnost povečala osemkrat glede na čisto PCM spojino in čisti nosilni material. The problem of high fossil fuel and electricity consumption for operation of air conditioners and space heating can be solved by replacing them with the energy storage materials. Certain materials can absorb and release thermal energy when it is necessary. The most favourable are the materials, which can store the latent heat, as the heat required to change the temperature is stored, as well as the heat required to change the physical state of the phase change materials (PCM). The melting temperature of PCM determines the field of application of composite material, which means, that the PCMs which have melting temperature in the room temperature range (25℃), are the most suitable for use in the residential buildings. Most often these are paraffin waxes and fatty acids. These compounds must be properly incorporated into the carrier material/matrix in order to maximize efficiency and to prevent fire, as the organic compounds are flammable. A suitable method of incorporating is shape stabilization of PCM in the matrix at elevated temperature, then cool below the glass transition temperature. Composite materials for latent heat storage have low thermal conductivity. Therefore, carbon-based materials (dopants) are added. In addition to improve thermal conductivity, dopants also provide better stability of PCM in the matrix. In this thesis are described both examples of the use of carbon-based dopants in composite materials for latent heat storage. Morphology, thermal and mechanical properties and thermal conductivity of these materials are mainly discussed. According to the results obtained from the literature, composite materials for latent energy storage are stabile after a number of heating and cooling cycles. Melting point and glass transition temperature of the matrix are maintained and are independent of the concentration of dopants. The matrix is stable at the melting temperature of the PCM, which means, that it can retain the PCM, when it is in a liquid state and prevent leakage. The amount of stored latent energy is high enough for practical use and is between 100 J/g and 200 J/g, depending on the proportion of each component. In the case of mixture of 0,8 wt.% graphene oxide with 19,2 wt.% matrix (mixture of wood powder and polyurethane) and 1,2 wt.% graphene oxide with 18,8 wt.% matrix, the thermal conductivity increased eightfold compared to pure PCM and pure matrix.

Sodobni trendi na področju industrije spodbujajo k uporabi obnovljivih in biorazgradljivih materialov, ki so trajnostni in imajo čim manjši vpliv na okolje. Ko je govora o materialih, se vse pogosteje posega na področje nanomaterialov, ki imajo izboljšane lastnosti in večjo aplikativno vrednost. Med temi materiali so hidrogeli na osnovi različnih polimerov, ki se v farmacevtski industriji uporabljajo za tarčno in kontrolirano sproščanje učinkovin v telesu. V sklopu magistrskega dela sem preučeval vpliv strukture hidrogelov na osnovi TEMPO modificirane nanofibrilne celuloze in skleroglukana na reološke lastnosti ter spremljal sproščanje nikotina iz teh hidrogelov. Ugotovil sem, da sta starost in koncentracija pomembna parametra, ki vplivata na strukturo hidrogelov, njun vpliv pa je mogoče preučevati preko reoloških lastnosti. Ugotovil sem, da je poleg strukture hidrogela ključen faktor pri sproščanju spojine interakcija med hidrogelom in spojino. Current trends in industry promote use of renewable and biodegradable materials that are sustainable and have a minimal impact on the environment. When it comes to materials, there is an increasing involvement in the field of nanomaterials, which have improved properties and increased applicative value. Among these materials are hydrogels based on various polymers used in the pharmaceutical industry for targeted and controlled drug release. As part of my master's thesis, I studied the effect of composition of hydrogels from TEMPO-oxidized nanofibrillated cellulose and scleroglucan on rheological properties and release of nicotine from hydrogels based on these materials. I have concluded that ageing time and concentration are important parameters that affect the structure of hydrogels, and their influence can be studied through rheological properties. I have concluded that, in addition to the hydrogel structure, a key factor in the release of a compound is the interaction between the hydrogel and the compound.

Hibridni kompoziti na osnovi naravnih vlaken so snovi, ki vsebujejo več različnih vlaken. Sestavljeni so iz polimerne matrice ter vsaj dveh polnil, od katerih so vsaj eno polnilo vlakna naravnega izvora. Lastnosti kompozita so odvisne od lastnosti posameznih komponent in interakcij med njimi. Namen uporabe naravnih vlaken v teh kompozitih so njihove dobre mehanske lastnosti, dostopnost, cena, nizka gostota, prijaznost okolju, pri predelavi pa ne sproščajo nevarnih snovi in zaradi tega ne poškodujejo opreme, ki se pri predelavi uporablja. Za naravna vlakna pa so značilne tudi slabosti, kot so slaba termična obstojnost, gorljivost, absorpcija vode in občutljivost na UV svetlobo, mikrobe in plesni. Tem slabostim se lahko izognemo na nekaj načinov. Kot prvo, lahko naravna vlakna dodatno obdelamo, s čimer spremenimo njihov značaj in lažjo vezavo z matrico. Kot drugo pa lahko kompozitu dodamo še eno ali več polnil. Dodatno polnilo omili slabosti naravnega polnila. Na ta način lahko pripravimo kompozite z lastnostmi čim bližje takim kot si jih želimo in s tem omogočimo njihovo uporabo na določenem področju. Natural fiber hybrid composites are substances containing different fibers. They are made of polymer matrix and at least two fillers, where at least one filler is natural fiber. Properties of a composite depend on properties of each component and interactions between them. Purpose for the use of natural fibers are their great mechanical properties, accessibility, price, low density, environmental friendliness, and they do not release harmful substances during processing, that can damage the equipment used. Natural fibers also have some weaknesses, such as bad thermal stability, flammability, water absorption, sensitivity to UV light, germs and molds. There are a few ways to void these. Firstly, we can additionally process natural fibers to improve their properties and matrix bonding. Secondly, we can add more fillers to the composite. The additional filler lessens the weaknesses of the natural filler. That way we can make composites with properties close to the wanted ones and enable their use for a certain application.